Do Human Leukocyte Antigens (HLAs) determine attraction between humans?

HLA and Human Attraction: Current Scientific Evidence

There is limited scientific evidence suggesting that HLA similarity may influence attraction between humans, primarily through olfactory mechanisms, but this effect appears to be modest and influenced by multiple factors including hormonal contraceptive use.

HLA System and Its Primary Functions

Human Leukocyte Antigens (HLAs) are a complex group of genes on chromosome 6 that encode proteins crucial for immune function:

• HLAs are primarily involved in presenting antigens to T cells, influencing the adaptive immune response 1
• The MHC (Major Histocompatibility Complex) locus, which includes HLA genes, is associated with more complex diseases than any other locus in the human genome 1
• HLA molecules are divided into class I (HLA-A, HLA-B, HLA-C) and class II (including HLA-DR, HLA-DQ, HLA-DP) 2

Evidence for HLA's Role in Human Attraction

Several studies have investigated the relationship between HLA and human attraction:

• Women not using hormonal contraception found body odors from HLA-B and HLA-C similar donors significantly less attractive than those from HLA-dissimilar donors 3
• HLA dissimilarity has been correlated with partnership satisfaction, sexuality, and desire to procreate in a large sample (N=508) with high-resolution typing of HLA class I/II 4
• As the proportion of shared MHC alleles increased between couples (N=48), women's sexual responsivity to their partners decreased, and their attraction to men other than their primary partners increased 5

Biological Mechanisms and Evolutionary Perspective

The potential mechanism for HLA-based attraction appears to be primarily olfactory:

• Olfactory receptor genes have been mapped to the HLA region, providing a potential mechanism for HLA-based odor recognition 6
• This preference may serve an evolutionarily adaptive function by:
  • Preventing offspring from having decreased immunocompetence
  • Decreasing the chance of kin mating 3
  • Maintaining MHC diversity in natural populations 7

Factors Influencing HLA-Based Attraction

The strength and direction of HLA-based attraction is not uniform and can be modulated by:

• Hormonal contraceptive use: Women using hormonal contraceptives do not exhibit significant HLA-related preferences 3
• Genetic background: Individual genetic factors beyond HLA may influence mate preference 7
• Sex differences: Effects appear more pronounced in women than men 3, 5
• Early life experience: May modulate HLA-based preferences 7

Clinical and Practical Implications

While interesting from an evolutionary and biological perspective, the clinical relevance of HLA-based attraction remains limited:

• HLA typing has more established value in transplantation medicine and autoimmune disease risk assessment than in relationship counseling 2
• The effect size of HLA-based attraction appears modest compared to social, cultural, and psychological factors that influence human mate choice
• Current evidence does not support using HLA typing as a basis for matchmaking services

Limitations of Current Research

The research on HLA and human attraction has several limitations:

• Sample sizes in many studies are relatively small
• Difficulty controlling for confounding variables in human mate choice
• Potential publication bias favoring positive findings
• Limited replication of key findings across diverse populations

In conclusion, while there is evidence suggesting HLA may play a role in human attraction through olfactory mechanisms, this represents just one of many factors in the complex process of human mate selection, and its practical significance remains uncertain.